Of all the happenings in Lyons Cathedral, the most momentous was the Ecumenical Council of 1274. Christendom never witnessed a greater gathering. At the Council held at Lyons in 1245, Innocent IV had preached his famous sermon on the five wounds of the Church, but he was less concerned with healing them than with excommunicating Frederick II. St. Louis tried in vain to make peace between pope and emperor on his visit to Lyons in those days. When the saint-king died on his last crusade his ashes rested in honor in Lyons Cathedral on their long journey from Tunis to St. Denis. Till the death of Frederick II, the pope lived in Lyons, whose independent position, neither wholly of France nor of the Empire, caused it to be a chosen spot for exiles. Innocent contributed toward the building of a stone bridge over the Rhone to replace one that had collapsed under the troops of Philippe-Auguste and Coeur-de-Lion as they marched to the Third Crusade.
The Council of 1245 had been held in a cathedral of whose nave only four bays were completed. For the far greater gathering of 1274, Lyons Cathedral could seat over two thousand prelates and princes. The chief visitors were placed in the choir with Gregory X (formerly a canon of this church). Among them was Aragon's king, Jaime el Conquistador, mighty builder of churches and untiring crusader, Guy de la Tour, the bishop-builder of Clermont Cathedral, and the bishop of Mende, Guillaume Durandus, author of the universally read liturgical treatise. St. Bonaventure, whose book of meditations was soon to inspire Giotto, preached at the opening Mass. His fellow teacher in Paris University, St. Thomas Aquinas, journeying north to attend the congress at Lyons, had died suddenly in the prime of life.
The Council of 1274 was not political, as had been that of 1245; its main purposes were the Holy War in the East and the reconciliation of the Greek and Latin churches. The Emperor of Constantinople had sent officials to reconcile him with Rome, and to this day memorials of that short reunion--Greek and Latin processional crosses--stand behind the chief altar of Lyons Cathedral. The emperor's ambassadors solemnly abjured the twenty-six propositions condemned by Rome, then took the oath of fidelity to the pope. With swelling heart the vast throng rose to chant the _Te Deum_. Gregory X intoned the _Credo_ in Latin, and the Greek patriarch repeated thrice the _Filioque_ phrase which, centuries earlier, had been the occasion of the break with Rome, _qui ex Patre Filioque procedit_. Before the century ended the union was a dead-letter, though the emperor till his death remained faithful to his pact. The Greek priesthood proved irreconcilable.